Tape printing apparatus

ABSTRACT

The invention relates to a tape printing apparatus for printing an image on an image receiving tape. In order to detect characteristics of the tape thus avoiding representation means on a tape cassette, it is proposed to have detecting means for detecting-markings provided on the image receiving tape, which provide information on a characteristic of the tape; and the tape printing apparatus is controlled in accordance with the detected characteristics. Alternatively, it is proposed to have monitoring means for monitoring the speed of the image receiving tape, which detect marking on the image receiving tape whereby the printing means is controlled in dependence on the detected speed. Consequently, the exact tape speed is considered for printing purposes, even when slippage between driving means and tape occurs.

FIELD OF THE INVENTION

The present invention relates to a tape printing apparatus and, inparticular, but not exclusively, is concerned with a drive system for atape printing apparatus. The present invention also relates to a supplyof image receiving tape for a tape printing apparatus.

BACKGROUND OF THE INVENTION

Known tape printing apparatus of the type with which the presentinvention is generally concerned are disclosed in European Patents,EP-A-322918 and EP-A-322919 (Brother Kogyo Kabushiki Kaisha) andEuropean Patent EP-A-267890 (Varitronic). The tape printing apparatushave a cassette receiving bay for receiving a cassette or tape holdingcase. In EP-A-267890, the tape holding case houses an ink ribbon and asubstrate tape, the latter comprising an upper image receiving layersecured to a backing layer by an adhesive. In EP-A-322918 andEP-A-322919, the tape holding case houses an ink ribbon, a transparentimage receiving tape and a double-sided adhesive tape which is securedat one of its adhesive coated sides to the image receiving tape afterprinting and which has a backing layer peelable from its other adhesivecoated side. With both these apparatus, the image transfer medium (inkribbon) and the image receiving tape (substrate) are in the samecassette.

In all of these apparatus, the image receiving tape passes in an overlapmatter with the ink ribbon to a print zone consisting of a fixed printhead and a platen against which the print head can be pressed to causean image to transfer from the ink ribbon to the image receiving tape.There are many ways of doing this, including dry lettering or dry filmimpression, but the most usual way at present is by thermal printingwhere the print head is heated and the heat causes ink from the inkribbon to be transferred to the image receiving tape. Alternatively, theprint head may be in direct contact with a thermally sensitive imagereceiving tape whereby when the print head is heated, an image isdefined directly on the image receiving tape, without the need for anink ribbon.

The known tape printing apparatus have input means, for example, akeyboard to allow the user to input an image to be printed. A displaymay be provided to display the input image and/or messages to the user.A cutting arrangement is provided to separate the image receiving tapeon which an image has been printed from the supply of image receivingtape to thereby define a label.

European Patents EP-A-575772 (Esselte Meto International ProduktionsGmbH) discloses a thermal printer arranged to print bar code informationor the like on discrete labels. The discrete labels may be supported ona backing sheet. Markings to identify the characteristics of the labelmay be provided either on the label itself or on the backing sheet. Themarkings, if provided on the label, are invisible. The markings are readby the thermal printer and may be used to determine whether an imageshould be printed directly on the label by the thermal printer orwhether an ink ribbon is required to print an image on the label.

U.S. Pat. No. 4,531,850 (K.K. Sato) describes a printer which isarranged to print an image on a plurality of discrete labels carried ona backing web. Each label on the backing web has a mark thereon which isused to control the timing of the printing. In other words, the signalresulting from the detection of the marks on each label is used tocontrol when the printer is activated so that the image falls within thelabel boundaries. Thus, a signal is sent to a control unit connectedwith a thermal head and the printing operations are conducted inresponse to the instructions coming from the control unit. The labelmaybe temporarily halted during printing.

Published International Application WO 96/04142 (Laser Master Corp.)describes a printer having the capability of multiple colour printing.Accordingly, a locating pattern is provided on the image receiving mediato ensure that subsequent layers of colour correctly overlie previouslayers. The markings on the print media are used to determine whereprinting should take place.

British Patent GB-A-2228449 (Tokyo Electric Co. Ltd.) discloses an inkribbon for use in multiple colour printing. The ink ribbon has aplurality of colours sequentially aligned along the tape. Between theregions of different colours, colour recognition marks are provided so that the next colour can be identified. A plurality of evenly spacedmarkings are also provided on the tape from which the ribbon speed isdetermined. The speed of the ribbon varies as the ribbon spool is drivenat a constant speed. The speed of the ink ribbon is used to correctreadings obtained from the colour recognition marks so that the correctcolour can be determined.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda tape printing apparatus for printing an image on an image receivingtape, the apparatus comprising:

input means for receiving data defining an image to be printed on theimage receiving tape;

receiving means for receiving a supply of image receiving tape;

printing means for printing an image on the image receiving tape;

detecting means for detecting markings provided on the image receivingtape, the markings being arranged to provide information on acharacteristic of the image receiving tape; and

control means for controlling the tape printing apparatus in accordancewith the detected image receiving tape characteristic.

Thus, it is possible to use the signals provided by the detecting meansfor controlling the printing apparatus in accordance with the detectedimage receiving tape characteristics. The image receiving tape may beprovided with markings indicating, e.g. the tape width and/or printingenergy required for obtaining optimal printing results. The tape printercan thus size the image to be printed according to the detected tapewidth and/or select the printhead energy appropriately. Further, themarkings can represent tape background color, tape printing color ortape length. The latter characteristics will be primarily used fordisplay purposes, informing the user about the parameters of the tape heis using. This aspect of the invention allows to dispense withrepresentation means in a cassette (as disclosed, e.g. in EP-A-497352 orEP-A-534794) or in a tape replacement unit, as disclosed, e.g. inEP-A-635375, since only the image receiving tape as such is necessaryfor detecting the markings and hence controlling the printer. Theinvention is consequently applicable for image receiving tape providedin cassettes, and in replacement spools without any cassette, as well.

According to a second aspect of the present invention, there is provideda tape printing apparatus for printing an image on an image receivingtape, the apparatus comprising:

input means for receiving data defining an image to be printed on theimage receiving tape;

receiving means for receiving a supply of the image receiving tape;

printing means for printing an image on the image receiving tape inaccordance with the input data, the printing means being controlled bycontrol means;

a drive system operable to drive the image receiving tape past theprinting means; and

monitoring means for monitoring the speed of the image receiving tape,the monitoring means being arranged to detect markings provided on theimage receiving tape and to provide a signal indicative of the speed atwhich the image receiving tape moves past the printing means, themonitoring means being connected to the control means for the printingmeans whereby the printing means is controlled in dependence on thespeed of the tape.

By controlling the print head in dependence on the speed of the imagereceiving tape, it can be ensured that variations in the speed of thedrive system or slippage between the drive system and the imagereceiving tape do not have an adverse effect on the printing. As theprinting is controlled in dependence on the measured speed of the tape,variations in the speed of the tape are compensated for by the printingmeans. Furthermore, a direct correlation between the speed of the imagereceiving tape and the printing of the image thereon can be achieved.

Preferably, the drive system comprises a motor. The drive system maycontinuously drive the image receiving tape past the printing means.Alternatively, the image receiving tape may be driven stepwise past theprinting means.

The motor may be a dc motor. However, any other suitable type of motorcan also be used in embodiments of the present invention.

The input means may be in the form of a keyboard or the like oralternatively may be an input to receive a data stream from a computeror the like.

The markings may be detectable with electromagnetic radiation and themonitoring means preferably comprises a source of electromagneticradiation and a detector to detect electromagnetic radiation from thesource, after the electromagnetic radiation has interacted with themarkings on the image receiving tape. The electromagnetic radiation canbe any suitable type of radiation such as visible light, ultra violetlight or infra-red radiation. The detector can be arranged to detectradiation transmitted through the image receiving tape or reflectedtherefrom.

The electromagnetic radiation source may comprise a light emitting diodeand the detector may comprise a photo transistor. Thus, a cheap, yeteffective, monitoring means can be achieved.

Preferably, a grating member is arranged between the detector and theimage receiving tape, the grating member having at least one opening, oreach opening of the grating may substantially correspond in size andshape to a single marking. It has been found that such a grating memberimproves the signal provided by the detector. Without the presence ofthe grating member, the signal provided by the monitoring means may beunsatisfactory or require increased manipulation. The grating member mayenhance the differentiation between the markings and the surroundingregions so that a clearer signal is provided by the monitoring means.For example, where the markings are in the form of dark lines on a lightbackground (or vice versa) the contrast between the light and darkregions is emphasised by the use of a grating member. In one preferredembodiment of the present invention, a plurality of openings areprovided in the grating member. The spacing between adjacent openingspreferably substantially corresponds to the spacing between adjacentmarkings on the image receiving tape. It is preferably that the width ofeach marking, the width of the space between each adjacent pair of linesand the width of each opening of the grating are the same.

In an alternative embodiment of the present invention, the monitoringmeans is operable to detect magnetic markings on the image receivingtape. The magnetic markings may be defined on the image receiving tapewith magnetic ink, and the monitoring means may be operable to detectthe markings defined by the magnetic ink. Alternatively, the magneticmarkings may comprise a plurality of lines formed by recording fluxreversals onto a magnetic strip on the image receiving tape, themonitoring means being arranged to detect the lines defined on themagnetic strip.

In the above described embodiments, the markings are preferably in theform of evenly spaced parallel lines extending perpendicular to thelength of the image receiving tape. However, the markings may take anyother suitable form. For example, the markings may be in the form ofevenly spaced parallel lines extending at an angle to the length of theimage receiving tape.

In one embodiment, at least one characteristic of the markings at ornear an end of the image receiving tape is changed, the monitoring meansbeing arranged to provide a signal indicative of the change in thecharacteristic of the markings to the control means so that an end ofimage receiving tape condition is determined. The characteristic of themarkings which is changed may be one or more of the followingcharacteristics: pitch of markings; width of each marking; color; andreflectivity of markings. In an alternative embodiment, an end of tapecondition can be determined by the monitoring means if there is a lackof markings near or at the end of the image receiving tape.

In an alternative arrangement, the end of the image receiving tape isprovided with means for resisting the separation from a supply reel forthe image receiving tape, the monitoring means being arranged to providea signal indicative of the reduction in speed of the image receivingtape caused by the resisting means at the end of the image receivingtape so that an end of tape condition is determined.

Thus, the markings provided on the image receiving tape can also be usedin order to determine an end of tape condition as well as to control theprinting. In the first described arrangement, the lack of or change inmarkings provides an indication of an end of tape condition, whereas inthe second described arrangement, the reduction in detected speed of theimage receiving tape provides an indication of the end of tapecondition.

The markings on the image receiving tape are preferably arranged to alsoprovide information as to the characteristics of the image receivingtape, the monitoring means being arranged to detect different markingson different types of image receiving tape and to provide a signalindicative of the different markings so that the characteristics of theimage receiving tape are identified. These characteristics can includeone or more of the following:

tape size;

tape color; and

nature of the image receiving tape such as whether or not an ink ribbonis required in order to print an image on the image receiving tape or ifan image can be printed directly onto the image receiving tape withoutthe need for an ink ribbon. The operation of the tape printing apparatuscan be altered in dependence upon the detected characteristics of theimage receiving tape. The pitch of the markings, the width of themarkings, the color of the markings and/or the reflectivity of themarkings on the image receiving tape may be varied in dependence on thecharacteristics of the tape, the monitoring means being arranged toprovide a signal indicative of the detected markings. For example, whenthe speed of the image receiving tape is known (either detected eg. byan encoder on the shaft of the motor driving the tape, or determined bydriving the motor with the appropriate parameters, eg. a stepper motordriven with a certain frequency of driving pulses), it is easily tojudge from the frequency of detected pulses the pitch of the markings.

The tape printing apparatus is thus able to determine the nature of theinserted type of tape and control the operation of the apparatusaccordingly. The apparatus may be arranged to store the information onthe characteristics of the tape and only to carry out further checkswhen it is determined that the supply of image receiving tape may havebeen changed. For example, checks may only be carried out when it isdetected that a lid to the tape receiving means has been opened or asupply of image receiving tape has been removed from the receiving meansand replaced.

The drive system may be arranged to drive the image receiving tapebackwards after a first image has been printed thereon, and when theimage receiving tape is driven forwards again by the drive system asecond image may be printed on the image receiving tape overlying thefirst image, the markings on the image receiving tape being used toposition the image receiving tape so that the first and second imagesoverlie one another. This feature is particularly advantageous for thoseembodiments where multi-color images are required so that images of morethan one color overlie one another. In particular, full color printingcan be achieved using this technique by using three images, one on topof each other, in cyan, magenta and yellow. Additionally, a furtherimage in black may also overlie the first three images. Of course twotone printing can also be achieved with this technique. The number ofimages which overlie one another and the number of different colors canbe selected as required by the user. Additionally, any color can beselected for the images which overlie one another.

Counting means may be provided for counting the number of markings whichpass a given location when the tape is driven past the printing means inthe forward direction and for counting the number of markings which passthe given location when the image receiving tape is driven backwards,the counting means being arranged to stop the driving of the imagereceiving tape in the backwards direction by the drive system when thenumber of markings which have passed the counting means substantiallyequals the number of markings counted when the image receiving tape isdriven past the printing means in the forwards direction. In this way,an exact overlying of different images may be achieved. The countingmeans may comprise the monitoring means and the control means. Thecontrol means may A count the number of signals provided by themonitoring means. The control means may thus also control the drivesystem.

The printing means preferably comprises a thermal print head having agroup of printing elements to which pixel data defining the image to beprinted is passed sequentially on a group-by- group basis by the controlmeans, the groups being sequentially printed adjacent one another in thedirection of movement of the image receiving tape. Preferably, thesequential printing of the image on the image receiving tape iscontrolled by the control means in dependence on the speed of the imagereceiving tape. In this way, a correspondence between the speed of theimage receiving tape and the control of the print head may be achieved.

Speed control means may be provided to control the speed of rotation ofthe motor to be at an approximately constant level. The speed controlmeans may be coupled to the monitoring means, whereby the speed of themotor is controlled in dependence on the detected speed of the imagereceiving tape.

Preferably, the speed control means controls the speed of rotation ofthe motor to maintain the approximately constant level by applying amaximum drive to the motor if the speed of the image receiving tapedetected by the monitoring means falls below a first predeterminedvalue, no drive if the speed of the image receiving tape exceeds asecond predetermined value and a linear drive versus speedcharacteristic if the speed of the image receiving tape is between thefirst and second predetermined values. With this relatively simplealgorithm, it is possible to effectively control the speed of the motorwithin the bounds required by embodiments of the present invention. Itshould be appreciated that the speed of the image receiving tapeprovides a measure of the speed of the motor although, depending on theconstruction of any gear train between the motor and the drive for theimage receiving tape, the speed of the image receiving tape may behigher or lower than the speed of rotation of the motor.

The monitoring means may be arranged to detect when a supply of imagereceiving tape is not present and to provide a signal indicativethereof.

The monitoring means may be arranged downstream of the printing meansbut is preferably arranged upstream thereof. Upstream of the printingmeans, the tape is under tension and accordingly there is less variationin its speed and position. Thus, more accurate speed and printingcontrol can be achieved.

According to a third aspect of the present invention, there is provideda supply of image receiving tape arranged for use in a tape printingapparatus so that the image receiving tape can be driven past a printlocation and an image printed thereon, the image receiving tapecomprising a continuous printing layer having a top printing surface forreceiving a printed image and a rear adhesive surface and a continuousbacking layer removable to uncover the rear adhesive surface of the topprinting layer, the image receiving tape carrying along its lengthregularly spaced detectable markings to provide an indication of thespeed at which the image receiving tape is driven past the printinglocation or an indication of a characteristic of the image receivingtape.

Preferably, the markings comprise a plurality of evenly spaced lines.The marking may be of a contrasting color to the color of the surface ofthe image receiving tape on which the markings are provided. Themarkings provided on the image receiving tape may be detectable byelectromagnetic radiation. Alternatively, the markings may be magnetic.The magnetic markings may be defined by magnetic ink or the imagereceiving tape may include a magnetic strip on which the markings aredefined. The markings may be provided on the surface of the imagereceiving tape on which an image is printed. Such markings arepreferably invisible. However, the markings are preferably provided onthe continuous backing layer. The location of markings on the backinglayer may make it easier for the tape printing apparatus in which thesupply is received to detect the markings, without interfering with theprinting means. Additionally, if the markings are in any way heatsensitive, they are less likely to be effected if they are on thecontinuous backing layer which is further from the thermal print headthan the layer on which the image is defined.

The supply of image receiving tape may be housed in a cassette.Preferably, at least one of the following marking parameters is used toprovide information on the characteristics of the tape:

marking pitch; marking color; marking thickness; and markingreflectivity.

Preferably, a characteristic parameter of the markings is changed nearan end of the image receiving tape to provide an end of tape indication.

According to a fourth aspect of the present invention, there is providedin combination, a tape printing apparatus for printing an image on animage receiving tape and a supply of image receiving tape, the imagereceiving tape comprising a surface for receiving a printed image andcarrying along its length regularly spaced detectable markings, the tapeprinting apparatus comprising:

input means for inputting data defining an image to be printed on theimage receiving tape;

receiving means in which the supply of the image receiving tape isreceived;

printing means for printing an image on the image receiving tape inaccordance with the input data, the printing means being controlled bycontrol means;

a drive system operable to drive the image receiving tape past theprinting means; and

means for monitoring characteristics of the tape, whereby the monitoringmeans is arranged to detect the markings provided on the image receivingtape and provide a signal indicative of a parameter with which themarkings move past the printing means, the monitoring means beingconnected to the control means for the print head so that the printingmeans is controlled in dependence on the characteristics of the imagereceiving tape.

According to a fifth aspect of the present invention, there is providedin combination, a tape printing apparatus for printing an image on animage receiving tape and a supply of image receiving tape, the imagereceiving tape comprising a surface for receiving a printed image andcarrying along its length regularly spaced detectable markings, the tapeprinting apparatus comprising:

input means for inputting data defining an image to be printed on theimage receiving tape;

receiving means in which the supply of the image receiving tape isreceived;

printing means for printing an image on the image receiving tape inaccordance with the input data, the printing means being controlled bycontrol means;

a drive system operable to drive the image receiving tape past theprinting means; and

means for monitoring the speed of the image receiving tape, whereby themonitoring means is arranged to detect the markings provided on theimage receiving tape and provide a signal indicative of the speed atwhich the image receiving tape moves past the printing means, themonitoring means being connected to the control means for the print headso that the printing means is controlled in dependence on the speed ofthe image receiving tape.

According to a sixth aspect of the present invention, there is provideda method of operating a method of operating a tape printing apparatuscomprising input means for inputting data, receiving means for receivinga supply of image receiving tape and printing means for printing animage on image receiving tape, the method comprising the steps of:

inputting data defining the image to be printed via the input means;

driving the image receiving tape past the printing means;

detecting markings provided on the image receiving tape to therebydetermine a characteristic of the image receiving tape; and

controlling the printing of the image on the image receiving tape by theprinting means in dependence on the characteristic of the imagereceiving tape.

According to a seventh aspect of the present invention, there isprovided a method of operating a tape printing apparatus comprisinginput means for inputting data, receiving means for receiving a supplyof image receiving tape and printing means for printing an image onimage receiving tape, the method comprising the steps of:

inputting data defining the image to be printed via the input means;

driving the image receiving tape past the printing means;

detecting markings provided on the image receiving tape to therebydetermine the speed of the image receiving tape; and

controlling the printing of the image on the image receiving tape by theprinting means in dependence on the speed of the image receiving tape.

According to a eighth aspect of the present invention, there is provideda tape printing apparatus for printing an image on an image receivingtape comprising:

means for receiving a supply of image receiving tape;

printing means for printing an image on the image receiving tape;

detecting means for detecting markings provided on the image receivingtape, the markings providing information on at least one characteristicof the image receiving tape, the detecting means comprising a source ofelectromagnetic radiation, a detector and a grating.

Preferably, the grating is provided between the detector and the imagereceiving tape.

The at least one characteristic of the tape includes one or more of thefollowing characteristics:

tape speed; tape width; tape size; tape color; and printing methodrequired to print an image for example whether or not an ink ribbon isrequired or if the image receiving tape is a direct thermal material.

According to a ninth aspect of the present invention, there is provideda tape printing apparatus for printing an image on an image receivingtape comprising:

means for receiving a supply of image receiving tape and an ink ribbonfor providing an image on the image receiving tape;

printing means for printing an image on the image receiving tape usingthe ink ribbon;

detecting means for detecting markings provided on the ink ribbon, themarkings being arranged to provide information on a characteristic ofthe ribbon; and

control means for controlling the tape printing apparatus in accordancewith the detected ink ribbon characteristic.

The ink ribbon characteristic may be the speed of the ink ribbon; thecolour of the ink ribbon; size of the ink ribbon; and/or any otherproperty of the ink ribbon.

For a better understanding of the present invention and as to how thesame may be carried into effect, reference will now be made by way ofexample to the accompanying drawings

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the upper surface of a tape printingapparatus;

FIG. 2 is a view showing two cassettes inserted in the tape printingapparatus of FIG. 1;

FIG. 3 is a schematic view showing the elements of a drive systemembodying the present invention;

FIG. 4 is a schematic view of the rear surface of an image receivingtape embodying the present invention;

FIG. 5a shows a more detailed schematic view from above of a sensorarrangement, shown in FIG. 3;

FIG. 5b shows a schematic cross-sectional view along line A—A of FIG.5a;

FIG. 6 shows a signal produced by the sensor arrangement shown in FIG.3;

FIG. 7 shows a plan view of a single cassette inserted in a tapeprinting apparatus wherein markings are identifying a characteristic ofthe tape; and

FIG. 8 is a schematic view showing the elements of a drive system of theprinting apparatus according to FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a plan view of a tape printing apparatus 2. The tapeprinting apparatus 2 comprises a keyboard 4. The keyboard 4 has aplurality of data entry keys and in particular comprises a plurality ofnumbered, lettered and punctuation keys 6 for inputting data to beprinted as a label and function keys 8 for editing the input data. Thekeyboard 4 also comprises a print key 10 which is operated when it isdesired that a label be printed. Additionally, the keyboard 4 has anon/off key 12 for switching the tape printing apparatus 2 on and off.

A liquid crystal display (LCD) 14 is provided to display the data as itentered. The display 14 allows a user to view all or part of the labelto be printed which facilitated the editing of the label prior to itsprinting. The display 14 is also arranged to display various editingoptions which may be selectable by the user, for example using thefunction keys 8. Additionally, the display 14 can also display messagesto the user. The display 14 is driven by a display driver 16 which canbe seen in FIG. 3.

Next to the keyboard 4 of the tape printing apparatus 2, there is acassette receiving bay 18 which is arranged to receive two cassettes 20and 22 which are shown in FIG. 2. The cassette receiving bay 18 has alid 24 which is normally closed. FIG. 2 shows the interior of thecassette receiving bay 18 with the lid 24 removed. The cassettereceiving bay 18 includes a thermal print head 26 and a platen 28 whichcooperate to define a print zone 30. The platen 28 is mounted forrotation within a cage moulding 32. The print head 26 is pivotable abouta pivot point 34 so that it can be brought into contact with the platen28 for printing and moved away from the platen 28 to enable thecassettes 20 and 22 to be removed and replaced.

The first cassette 20 holds a supply spool 36 of image receiving tape38. The image receiving tape 38 comprises a continuous upper layer forreceiving a printed image on one of its surfaces and has its othersurface coated with an adhesive layer to which is secured a continuousreleasable backing layer. The image receiving tape 38 is guided by aguide mechanism (not shown) through the cassette 20, out of the cassette20 through an outlet O past the print zone 30 to a cutting location C.The platen 28 is accommodated in a recess 40 of the first cassette.

An opening 98 is provided in the first cassette 20 for accomodating asensor arrangement comprising a source 90 of electromagnetic radiationand a detector 92. This sensor arrangement will be described later withregard to FIG. 5. It is mounted to the frame of the printer 2, andallows detection of markings 70 (see FIG. 4) on the image receiving tape38.

The second cassette 22 has a supply of ink ribbon 42 on an ink ribbonsupply spool 44 and an ink ribbon take up spool 46. The second cassette22 also has a recess 48 for receiving the print head 26. The imagereceiving tape 38 and the ink ribbon 42 are arranged to pass in anoverlap manner between the print head 26 and the platen 28. Inparticular, the image receiving layer of the image receiving tape 38 isin contact with the ink ribbon 42. The ink ribbon 42 is a thermaltransfer ribbon which when in contact with the activated or heatedelements of the thermal print head 26 defines an image on the imagereceiving tape 38.

As will be described in more detail hereinafter, the platen 28 is drivenby a dc motor 50 (see FIG. 3) so that it rotates to drive the imagereceiving tape 38 in a direction which is parallel to the lengthwiseextent of the image receiving tape 38 through the print zone 30. In thisway, an image is printed on the image receiving tape 38 and the imagereceiving tape 38 on which an image has been printed is fed from theprint zone 30 to the cutting location C. The rotation of the platen 28also causes the ink ribbon 42 to be driven from the ink ribbon supplyspool 44, past the print head 26 and to the ink ribbon take up spool 46.

A cutting arrangement 52 is provided at the cutting location C whichincludes a cutter support member 54 carrying a blade 56. The blade 56acts against an anvil 58 to cut a printed label from the supply of imagereceiving tape 38.

The print head 26 is a thermal print head comprising a column of aplurality of printing elements. The print head 42 is preferably only oneprinting element wide and the column extends in a directionperpendicular to the lengthwise direction of the image receiving tape38. The height of the column of printing elements is preferably equal tothe width of the image receiving tape 38 to be used with the tapeprinting apparatus. With embodiments of this invention, where more thanone width of image receiving tape 38 is used, the print head column willgenerally have a height equal to the largest width of image receivingtape 38. An image is printed on the image receiving tape 38 column bycolumn by the print head 26. This will be described in more detailhereinafter. It should be appreciated that an image can be printed onthe image receiving tape via the ink ribbon 42. Alternatively, if theimage receiving tape 38 is of a suitable thermally sensitive material,an image can be applied by the print head 26 directly to the imagereceiving tape 38. No ink ribbon 42 would then be required with athermally sensitive image receiving tape 38, as shown in FIGS. 7 and 8.

It should also be appreciated that in some embodiments of the presentinvention, the tape printing apparatus 2 can be arranged to have twodifferent modes of operation. In the first mode of operation, an imageis applied directly by the print head 26 to the image receiving tape 38whilst in the second mode of operation, an image is applied to the imagereceiving tape 38 via an ink ribbon 42. Alternatively, the tape printingapparatus 2 may be arranged to print an image on the image receivingtape 38 only by directly applying an image to a thermally sensitiveimage receiving tape. This latter tape printing apparatus would then nothave a mode of operation in which an ink ribbon is used to define animage.

In some embodiments, the print head 26 may have a height which may beslightly less than the width of largest image receiving tape 38 whichcan be used with a tape printing apparatus 2. This is because an imageprinted on the image receiving tape 38 will usually have upper and lowerblank margins. The print head 26 may then have a height corresponding tothe largest width of image receiving tape 38, less the height of theupper and lower margins.

As an alternative to the two cassette systems shown in FIG. 2, thecassette receiving bay may be arranged to receive a single cassettehaving both the image receiving tape 38 and the ink ribbon 42. The inkribbon 42 can be dispensed with for those embodiments which are capableof printing an image directly on thermally sensitive image receivingtape 38. It should be appreciated that any suitable arrangement forproviding a supply of image receiving tape and/or ink ribbon can be usedwith embodiments of the present invention.

FIG. 3 shows the elements of a drive system according to one embodimentof the present invention. For clarity, only the platen 28 and print head26 are shown along with portions of the image receiving tape 38 and theink ribbon 42. The cassettes 20 and 22 for housing the ink ribbon 42 andthe image receiving tape 38 are not shown in this Figure. The platen 28is mounted for rotation about an axis 60 extending through the plane ofthe paper. The platen 28 rotates in the direction of arrow A. As can beseen from FIG. 3, the ink ribbon 42 and the image receiving tape 38 passin an overlap manner between the platen 28 and the print head 26. Asdiscussed previously, a dc motor 50 is provided. This is driven from amicrocontroller in the form of a microprocessor chip 62 via a currentbuffer 64 using pulse width modulation to approximate a linear controlvoltage for the dc motor 50 at its terminals 66 and 68. As iswell-known, a dc motor rotates continuously at a speed related to theapplied voltage. The rotation is continuous and not stepwise.

As can be seen from FIG. 4, the reverse surface (the surface oppositethat to which the image is applied) of the image receiving tape 38 isprovided with a plurality of markings in the form of parallel lines 70which are evenly spaced apart along a substantial portion if not theentire length of the image receiving tape 38. In one preferredembodiment, the width of each line 70 is the same in each space 71provided between adjacent lines 70. The surface on which the lines 70are arranged may be provided by the releasable backing layer of theimage receiving tape 38. A sensor arrangement 72 is arranged to supply apulse to the microprocessor chip 62 via feedback line 74 each time oneline 70 passes the sensor arrangement 72. The platen 28 is connected viagear train 76 (shown only schematically) to motor 50. Accordingly,rotation of the motor 50 drives the platen 28 which in turn drives theimage receiving tape 38. Thus, the speed of the image receiving tape 38is indicative of the speed of the motor 50. The microprocessor chip 62can therefore determine the speed of the motor 50 by measuring thefrequency of the pulses fed back to it along line 74 from the sensorarrangement 72. Alternatively or additionally, the microprocessor chip62 can determine the pitch of the lines 70 on the image receiving tape38 from the frequency of the signals provided by the sensor arrangement,when the speed of the motor is known. The speed of the motor can bedetermined by means of an encoder on the shaft of the motor, or when themotor is a stepper motor. The sensor arrangement 72 will be described inmore detail hereinafter.

A crystal oscillator 78 provides reference clock cycles for themicroprocessor chip 62. The microprocessor chip 62 supplies print dataalong line 80 to the thermal print head 26 which has a storage registerand a shift register (not shown). The storage register is separate fromthe shift register and arranged in parallel thereto. Data is transferredto the print head 26 serially, clocked bit by bit under the control ofthe microprocessor chip 62 to the shift register contained in the printhead 63. At the end of the transfer of a column of pixel data, the datais latched into the storage register under command from themicroprocessor chip 62. The storage register will hold this data untilthe next latching operation of the new shift register contents into thestorage register. Later, the print head 26 is “strobed” by themicroprocessor chip 62 to turn on high current output drivers inparallel which deposit melted ink from the ink ribbon 42 onto the imagereceiving tape 38 in pixel patterns according to data held in thestorage register. With a thermally sensitive image receiving tape 38,the heated printing elements are in direct contact with the imagereceiving tape 38. Clocking of data into the shift register can occurwhilst a strobe signal causes printing of the data in the storageregister, but it should be appreciated that this operation need notoccur in this way since the two operations are independent.

As explained above, the thermal print head 26 has a column of printingelements which are printed as a vertical line on the image receivingtape 38. A character is thus printed by printing a number of adjacentand slightly overlapping columns containing different pixel data on theimage receiving tape 38 as it moves past the print head 26. Thus, animage is defined on the image receiving tape 38 as the groups of pixeldata are sequentially printed adjacent one another in the direction inwhich the image receiving tape 38 is driven past the image receivingtape 38. Accordingly, the microprocessor chip 62 provides print strobesignals. On each print strobe signal, the column of data held in thestorage register is printed.

In some embodiments of the present invention, the print head is dividedinto a plurality of groups which are not operated at the same time. Withthis embodiment a separate strobe signal would be required for the datafor each group of printing elements of the print head. Thus, if theprint head is divided into three separate groups then three strobesignals will be required. As described hereinafter, each strobe signalmay only be provided when, for example two or more lines are detected.Thus, if the print head is divided into more than one group, anincreased number of signals from the sensing arrangement is required foreach print cycle. This means that the number of lines per inch on theimage receiving tape may need to be increased. The arrangementhereinafter described which uses a magnetic strip may be particularlyappropriate.

In FIG. 3, reference numeral 82 denotes a power supply for the currentbuffer 64 and the microprocessor chip 62. The power supply can be mainsor batteries.

The speed of the dc motor 50 is controlled by the microprocessor chip 62using an algorithm which measures the number of reference clock cyclesfrom the crystal oscillator 78 between successive pulses supplied by thesensor arrangement 72 to the microprocessor chip 62 along feedback line74. The value obtained from this measurement is used to calculate thespeed of the motor 50 and this in turn is used to alter the pulse widthof the pulse width modulated drive signal to the current buffer 64 toadjust the motor drive in a manner so as to hold the speed constant.

The dc motor 50 is arranged to have a speed of rotation at anapproximately constant level. By measuring the speed of the imagereceiving tape 38 or the motor 50 with the mentioned encoder on themotor shaft, it is possible to determine approximately the speed ofrotation of the dc motor 50. The microprocessor chip 62 controls thespeed of rotation of the dc motor 50 by causing a maximum drive to beapplied to the do motor 50 if the determined speed of the imagereceiving tape falls below a first predetermined value, no drive if thespeed exceeds a second predetermined value and a linear drive versusspeed characteristic if the determined speed for the image receivingtape falls between the first and second predetermined values. Thisresults in a simple speed control of the motor. Clearly as themicroprocessor chip 62 has knowledge of the approximate motor speed atall times, it can take appropriate action if the speed is outsidecertain limits.

The fact that there is only a somewhat coarse control of the speed ofthe dc motor 50 is not a disadvantage in embodiments of the presentinvention for the reason that print strobe signals which control theprinting of each column of data and the supply of the next column ofdata to the print head 26 is made responsive to the signals supplied bythe sensor arrangement 72 to the microprocessor chip 62. On each datastrobe signal supplied to the print head 26, a column of data stored inthe storage register of the thermal print head 26 is printed. At thenext strobe signal, the next column of data which has been transferredto the storage register from the shift register is printed. In this way,the deposition of the image on the image receiving tape 38 is related tothe motion of the image receiving tape 38. With embodiments of thepresent invention, significant speed variations have a negligible effecton print quality, as the print strobe signals supplied to the print headslow down or speed up in response to the actual speed of the imagereceiving tape.

In summary, the determined speed of the image receiving tape 38 is usedto control tho printing of an image on the image receiving tape 38 andalso to control the speed of the motor 50. This has the benefit that itis not necessary to have a complicated and potentially costly controllerfor accurate speed control. The system can therefore be implemented in alow cost general purpose microprocessor chip with little overhead todistract it from other tasks, such as handling the print data itself.

The microprocessor chip 62 has a read only memory (ROM) 84, amicroprocessor portion 86 and random access memory capacity indicateddiagrammatically by RAM 88. The microprocessor 86 is controlled byprogramming stored in the ROM 84 and when so controlled acts as acontroller. The microprocessor chip 62 is connected to receive labeldata input to it via the keyboard 4. The microprocessor chip 62 outputsdata to drive the display 14 via the display driver 16 to display alabel to be printed (or a part thereof) and/or messages or instructionsfor the user. The display driver 16 may alternatively form part of themicroprocessor chip 62. The microprocessor chip 62 may also control thecutting arrangement 52 to allow lengths of image receiving tape 38 to becut off after an image has been printed thereon.

The microprocessor chip 62 generates pixel data in accordance with datainput via the keyboard 4. As mentioned hereinbefore, this pixel data istransmitted column by column to the print head 26.

Reference will now be made to FIGS. 5a and 5 b which show a schematicview of the sensor arrangement 72. The sensor arrangement 72 comprises alight source 90 which may be a light emitting diode and a light detector92 which may be in the form of a photo transistor. The photo transistor92 is arranged to detect light emitted by the light source 90 which isreflected from the rear surface of the image receiving tape 38, that isthe surface on which the lines 70 are provided. The lines 70 willnormally be much darker than the background 71 of the image receivingtape 38. Accordingly, more light will be reflected from the lighterregions 71 between the lines 70 on the rear of the image receiving tape38 to the photo transistor 92. Conversely, when the light from the lightemitting diode 90 impinges on a line 70, which is darker than thebackground of the image receiving tape, much less light (if any) will bereflected back to the photo transistor 92.

The use of a grating 94 having a single slit 96 extending across thewidth of the image receiving tape 38 is advantageous in that a higherquality wave form is provided by the photo transistor 92, such as shownin FIG. 6. The width W of the slit 96 is selected so as to have a widthgenerally corresponding to the width of a single line 70. The space orlight regions 71 preferably each have a width equal to that of a singleline 70. However, this is not essential. The spaces or light regions 71may have a width greater or less than that of each line 70. Thus, thedimensions of the slit 96 corresponds generally to the dimensions of asingle line. When the slit 96 is positioned centrally over a line 70,only the line 70 can be seen through the slit 96. In FIG. 5b, a line 70is partially shown behind the slit as the line 70 is no longer centredon the slit 96. The provision of the grating improves the contrastbetween the light regions 71 and dark regions defined by the lines 70 onthe image receiving tape 38. This provides sharper peaks 93 and troughs95 in the wave form provided by the photo transistor 92, as shown inFIG. 6. As will be appreciated, the microprocessor chip 62 uses the timebetween successive peaks 93 or troughs 95 to make a determination of thespeed of the image receiving tape 38. One of the peaks 93 and troughs 95will represent the passing of lines 70 past the grating 94 whilst theother of the peaks 93 and troughs 95 will represent the passing a lightregion 71 past the grating 94.

In one modification to the above described grating, a plurality of slitsare provided. The spacing between adjacent slits corresponds to thedistance between adjacent markings on the image receiving tape. In otherwords, the pitch of the slits is the same as that of the lines 70 andthe light regions or spaces 71. This modification has the advantage thatmore light is transmitted back to the detector as compared toembodiments which only use a single slit. Thus, less sensitive and hencecheaper detectors can be used.

In another modification to the above-described arrangement the gratingopening need not be of the same width as the lines 70 and the spaces 71between those lines. In particular, the grating opening width may besmaller than the width of the lines 70 or the width of the spaces 71therebetween.

The grating is generally arranged between the image receiving tape andthe detector. However, in some embodiments, the grating may be arrangedon the opposite side of the image receiving tape to the detector. Thisarrangement may be used if the source and detector are on opposite sidesof the image receiving tape.

In one preferred embodiment of the present invention, a data strobesignal for controlling the print head 26 can be produced by themicroprocessor 62 for each peak 93 or trough 95 detected by the sensingarrangement 72. Alternatively, a data strobe signal can be produced forevery two peaks 93 or troughs 95 provided by the sensing arrangement 72or for any other integral number of peaks 93 or troughs 95. On each datastrobe signal, a column of data stored in the storage register of thethermal print head 26 is printed. At the next strobe signal, the nextcolumn of data which has been transferred to the storage register fromthe shift register is printed. In this way, the printing of the image onthe image receiving tape 38 is related exactly to the motion of thetape.

Typically, tape printing apparatus may print with a resolution of 180dots per inch (dpi). Thus if two pulses (two peaks or two troughs) arerequired from the sensing arrangement 72 for each strobe pulse, thelines 70 would need to be printed on the back of the image receivingtape along the length thereof with a resolution of 360 dots per inch. Inother words, 360 lines would need to be printed on each inch of imagereceiving tape 38. Alternatively, if only one pulse were to be providedfor each strobe pulse, the lines would have to be printed with aresolution of 180 dots per inch. If only a single pulse (one trough orone peak) from the sensor arrangement 72 is provided for each strobesignal, it is advantageous if the motor were to be run at a higher speedas compared to embodiments where two pulses are provided by the sensingarrangement 72 for each strobe signal. This is because at greater motorspeeds, the motor becomes easier to control and a single motor drivepulse per print cycle may be sufficient to control the motor. This isbecause the signal provided by the sensor arrangement is used to controlnot only printing but also the motor speed.

In one variation on the present invention, the lines 70 could be printedon the image receiving tape 38 with magnetic ink and magnetic sensorswould be used to detect the lines, in an analogous way to that describedin relation to the embodiment shown in FIG. 5. The magnetic markings onthe tape could be detected using a magnetic proximity detector. Themagnetic proximity detector may comprise a coil wound around a barmagnet. If a magnetic object such as a fine 70 defined by magnetic inkis moved past a pole of the magnet, the flux changes and a current isinduced in the coil. Thus, each time a line 70 defined by magnetic inkmoves past the coil, a pulse of current would be induced in the sensorcoil. The number of pulses can be counted in a similar way to the pulsesdescribed in relation to the previous embodiment.

In a further modification to the present invention, a continuousmagnetic strip could be attached to the rear of the image receiving tape38. Markings in the form of “lines” could then be recorded onto thestrip. Those lines are defined by recording flux reversals onto amagnetic strip. The resolution could vary between 100 flux reversals perinch to between 10,000 to 15,000 flux reversals per inch i.e. up to 600“lines” per millimetre. A higher resolution can therefore be obtainedusing such a magnetic strip. These magnetic markings can be detectedusing a magnetic head of the type used in audio or data recordingreading equipment. Such magnetic heads are well-known and will not bedescribed here.

The degree of resolution (number of markings per inch) required willdepend on a number of factors. In particular, the required resolutiondepends on the number of dots printed by the print head per inch alongthe length of the image receiving tape as well as the number of signalswhich need to be provided by the sensing sensor arrangement 72 for eachstrobe signal.

FIGS. 7 and 8 show a tape printer 2 capable of printing onto a directthermal tape medium serving as image receiving tape 38. In FIGS. 7 and8, same elements are denoted with like reference numerals. The inkribbon cassette 22 and the ink ribbon 42 shown in FIGS. 2 and 3 areremoved. Another important difference shown in FIG. 8 is that anadditional feedback line 106 connected to the microprocessor 86 iscoupled to an encoder arrangement which measures the speed of the dcmotor 50. The motor 50 is coupled via a gear train 76 with a rotatablysupported disc 100 provided with markings 102. Another gear train 76connects the disc 100 with the shaft 60 of the platen 28. An opticaldetector 104 is provided for detecting the markings 102 on disc 100.Consequently, the encoder arrangement consisting of disc 100 withmarkings 102 and detector 104 gives a pulse every time the a marking 102is detected. Thus, the motor speed is being measured. Consequently, themicroprocessor gets two inputs, the first one (line 106) giving aninformation about the speed of the motor 50, and the second one (line74) containing an information about the frequency (and amplitude andwaveform) with which markings 70 on the tape 38 are detected.Consequently, it is possible to use the markings 70 for detecting acharacteristic of the image receiving tape. Consequently, eg. the pitchof the markings 70 can be used for detecting a characteristic of theimage receiving tape, and for controlling the printing mechanismaccordingly. In other words, the signal from the sensing arrangement 72provides an indication of a characteristic of the image receiving tape38. Consequently, it would be possible to identify the width of the tape38 and to control the printing mechanism accordingly, ie. to sizecharacters such that they fit onto the tape. It should be noted that astepper motor could be provided instead of the dc motor 50, thusallowing to dispense with the disc 100 and the detector 104. Further,when a grating 94 is used in this embodiment of the invention, it isproposed to have multiple gratings 94 and detectors 92, wherein eachgrating has a different distance between its openings. Each grating 94is then assigned to a predetermined type of tape 38, whereby each typeof tapes has a pitch of markings 70 corresponding to the distancebetween the openings of the assigned grating 94.

In one modification of the present invention, an end of image receivingtape condition can be simply detected. In particular, at or near the endof the image receiving tape there may be no lines or markings. Theabsence of pulses (peaks or troughs) in the signal from the sensorarrangement 72 could be noted so that an end of tape condition could bedetermined by the microprocessor chip 62. The print head 26 would thenbe controlled to stop printing. A message advising the user of an end oftape condition can of course be displayed on the display 14.

In one preferred modification to the above embodiments, the pitch of thelines or markings on the tape is reduced or increased at or near the endof the tape. There is preferably a significant difference between thenormal pitch and the pitch of the lines or markings near the end of thetape. The microprocessor chip 62 would be able to detect this differencein pitch from the increased or decreased number of signals which itreceives from the sensor arrangement and determines that an end of tapecondition exists. This variation has the advantage that themicroprocessor chip 62 is able to distinguish between end of tapeconditions and a motor stall resulting from a tape jamming.

In one modification of the present invention, the signal provided by thesensing arrangement 70 along line 74 can provide an indication to themicroprocessor chip 62 of a motor stall condition (that is no rotationof the motor even with an applied voltage) or a partial stall, whichcould be due to faults such as a tape jam or a mechanism failure, or dueto the end of the tape being reached. Thus, the apparatus can be used toprovide an end of tape indication where the image receiving tape 38 issecured to its tape supply reel and is optionally provided with highfriction material at its end so that the end of tape condition ismanifested by a motor stall or partial stall. The stall condition iseasily determined by the microprocessor chip 62 in that no pulses (peaksor troughs) are provided by the sensor arrangement 72. Where highfriction material is provided at the end of the image receiving tape 38,the high friction material is in contact with the platen 28 and causesthe motor 50 to slow down and, finally, to stall because the end ofimage receiving tape 38 is secured to its supply reel and cannot move.The image receiving tape 38 is no longer driven, which is detected bythe sensor arrangement 72. Thus, a signal indicating that there is anend of tape condition is sent via line 74 to the microprocessor chip 62.In this latter embodiment, markings may be provided along the entirelength of image receiving tape including on the end region of the imagereceiving tape.

It should be appreciated that the line pitch, line thickness, linecolor, line reflectivity or indeed any other characteristic of themarkings provided on the image receiving tape can be varied depending onthe characteristic of the tape contained in the cassette 22. By varyingthe line pitch, fine thickness, line color or line reflectivity,information relating to color, tape width, and/or the nature of theimage receiving tape (i.e. whether or not an ink ribbon is required) canbe encoded on to the tape. The microprocessor chip 62 determines therelevant characteristic of the lines or markings and can thus determinethe characteristics of the image receiving tape present in the cassettereceiving bay.

Variations for example in line pitch could be detected by a gratinghaving a single opening. Preferably, the variation in line pitch wouldbe small as changes in the line pitch would result in a proportionalchange in the motor and print speeds. The change in the motor speed maybe detected by monitoring the current drawn by the motor, this beingindicative of the motor speed. The current drawn by the motor would thusprovide an indication of the line pitch and hence the information on thetape characteristics can be determined.

In a more preferred variation, the width of the lines, the color and/orthe reflectivity of the lines is varied. The overall timing informationin the waveform received by the microprocessor chip would be unchanged,but the form of the signal provided by the sensing arrangement wouldchange. In other words, the frequency of the signals would be unchangedbut the waveform would differ with different colored lines, differentwidths of line or different line reflectivities. The change in the formof the signal provided by the sensing arrangement can be detected andused to determine the nature of the tape in the cassette.

The above-described line variations can be used to determine one or moreof the following tape characteristics; tape width, tape color, nature oftape, i.e. thermally sensitive tapes or tape requiring an ink ribbon.

It should be appreciated that the width, color, reflectivity of thelines could be changed near the end of tape so that an end of tapecondition can be detected.

Additionally, the markings on the rear of the image receiving tape 38can be used to define positions on the image receiving tape. This can beimportant in embodiments of the present invention where the tape has tobe driven back into the tape printing apparatus 2 and driven past theprint head a number of times, for example as might be required toachieve color printing. Good quality color printing would depend on theaccurate re-positioning of the print head at the defined beginning orstart of the label before each pass of the same portion of the imagereceiving tape past the print head. This ensures that each differentlycolored image overlies exactly the preceding printed images. Theaccurate repositioning is achieved by counting the number of lines ormarkings which pass the print head when an image is printed and thencounting exactly the same number of lines or markings when driving thetape printing apparatus in the reverse direction. The reverse driving isthen stopped and the tape driven again in the forward direction whilstthe image in the next color is printed on an image receiving tape, overthe image in the first color. Full color printing can be achieved byprinting three images overlying each other in three different colors;cyan, magenta and yellow. An image can also be printed in black over thethree images in cyan, magenta and yellow which may improve the qualityof the full color image. It should be appreciated that this sametechnique can be used with any number of overlying images using anycolor. For example two tone printing could also be achieved using thistechnique.

It should be appreciated that the print head need not necessarilyinclude shift registers and storage registers. Instead, the data couldbe passed for example directly to the thermal print head printingelements from the microprocessor chip.

In the specific embodiment described, the speed of the image receivingtape is used to make a determination of the speed of rotation of themotor. However, it should be appreciated that due to gearing, the speedof the image receiving tape may in fact be smaller or larger than theactual speed of rotation of the motor. However, the microprocessor chipcan be programmed to take into account the actual difference in speedbetween the image receiving tape and the motor.

In the specific embodiment illustrated, the markings on the tape aredescribed as being parallel dark lines on a lighter background. Itshould be appreciated that it would of course be possible to havemarkings in the form of light lines on a dark background. The distancebetween successive lines will of course depend on the required lineresolution. In the preferred embodiment, a source of visible light isused as a light source and the light is reflected from the imagereceiving tape. However, it should be appreciated that any othersuitable form of electromagnetic radiation can also be used, such asultra violet light or infra-red radiation. Additionally, transmission ofthe electromagnetic radiation can be used to distinguish between themarkings and their background. The markings described in the illustratedembodiment have been shown as parallel lines extending perpendicular tothe length of the image receiving tape. However, the markings may takeany suitable form such as dots or the like. If the markings are in theform of lines, the lines need not extend perpendicular to the length ofthe image receiving tape but may extend at an angle thereto.

In the embodiment illustrated in FIG. 3, the sensor arrangement 72 isarranged downstream of the print head and the platen. Thus, the portionof the image receiving tape which passes the sensor arrangement 72 mayhave an image printed thereon. It could of course be possible to arrangethe sensor arrangement 72 upstream of the print head 26 and platen 28.Thus, the image receiving tape passing the sensor arrangement 72, inthis modification, would not have an image printed thereon. This latterarrangement has the advantage that the tape is under tension upstream ofthe print head 26 and accordingly, the speed and position of the imagereceiving tape are less likely to vary.

In the various embodiments described, the motor is described as being adc motor. However, it should be appreciated that any other suitable typeof motor can be used with embodiments of the present invention.

In a modification of the present invention, the markings may be providedon the ink ribbon instead of the image receiving tape. Such anarrangement can be used if a sensor arrangement cannot be included in aposition suitable for detecting markings on image receiving tape. Thespeed of the ink ribbon can be used as a measure of the speed of theimage receiving tape. In some embodiments of the present invention,there may be advantages in measuring the speed of the ink ribbon itself.

In one modification of the above described embodiments, the nature ofthe image receiving tape is determined from the markings and theinformation on the image receiving tape is stored. The operation of thetape printing apparatus may be modified in accordance with thecharacteristics of the image receiving tape present in the tape printingapparatus. No further checks to determine the nature of the imagereceiving tape will be carried out until a condition is detected whichmay reflect a possible change in the image receiving tape. For example,the tape printing apparatus may be arranged to detect when the lid isopened. When the lid is subsequently closed, the tape printing apparatusmay carry out checks in order to determine the nature of the imagereceiving tape. The opening and closing of the lid may be detected bymeans of a switch connected to the microprocessor. The switch could be,for example, closed when the lid was closed and open when the lid wasopened. Alternatively, means may be provided in the cassette receivingbay to determine when a supply of image receiving tape has been removedand subsequently replaced if it is detected that a cassette of imagereceiving tape has been removed and replaced, then the checks todetermine the nature of the image receiving tape can be carried out. Apressure switch may be provided in the cassette receiving bay todetermine whether or not a cassette of image receiving tape is presentor absent. Such a switch would of course be connected to themicroprocessor.

What is claimed is:
 1. A printing apparatus for printing an image on animage receiving tape, the apparatus comprising: input means forreceiving data defining an image to be printed on an image receivingtape; receiving means for receiving a supply of the image receivingtape; printing means for printing an image on the image receiving tapein accordance with the input data; control means configured to controlthe printing means; a drive system operable to drive the image receivingtape past the printing means; and monitoring means for monitoring thespeed of the image receiving tape, the monitoring mean; being arrangedto detect markings provided on the image receiving tape and to provide asignal indicative of the speed at which the image receiving tape movespast said printing means, the signal being supplied to the control meansfor controlling the printing means in dependence on the speed of thetape indicated by the signal.
 2. A tape printing apparatus as claimed inclaim 1, wherein the markings are detectable with electromagneticradiation, and the monitoring means comprises a source ofelectromagnetic radiation and a detector arranged to detectelectromagnetic radiation from said source, after the electromagneticradiation from the source has interacted with the markings on the imagereceiving tape.
 3. A tape printing apparatus as claimed in claim 2,wherein the electromagnetic radiation source comprises a light emittingdevice and the detector comprises a photo transistor.
 4. A tape printingapparatus as claimed in claim 2, further comprising: a grating memberarranged between the detector and the image receiving tape, the gratingmember having at least one opening.
 5. A tape printing apparatus asclaimed in claim 4, wherein each opening substantially corresponds insize and shape to a single marking.
 6. A tape printing apparatus asclaimed in claim 4, wherein the grating member has a plurality ofopenings, the spacing between adjacent openings of the grating memberbeing substantially the same as the spacing between adjacent markings onthe image receiving tape.
 7. A tape printing apparatus as claimed inclaim 1, wherein the monitoring means is operable to detect magneticmarkings on the image receiving tape.
 8. A tape printing apparatus asclaimed in claim 7, wherein the magnetic markings are defined on theimage receiving tape with magnetic ink and the monitoring means arearranged to detect the markings defined by the magnetic ink.
 9. A tapeprinting apparatus as claimed in claim 8, wherein the magnetic markingscomprise a plurality of lines formed by recording flux reversals onto amagnetic strip on the image receiving tape, the monitoring means beingarranged to detect the lines defined on said magnetic strip.
 10. A tapeprinting apparatus as claimed in claim 1, wherein at least onecharacteristic of the markings at or near an end of the image receivingtape is changed, said monitoring means being arranged to provide asignal indicative of the change in the markings to the control means sothat an end of image receiving tape condition is determined by thecontrol means.
 11. A tape printing apparatus as claimed in claim 1,wherein the end of the image receiving tape is provided with means forresisting the separation from a supply reel for the image receivingtape, the monitoring means being arranged to provide a signal indicativeof the reduction in speed of the image receiving tape caused by themeans for resisting at the end of the image receiving tape so that anend of image receiving tape condition is determined by said controlmeans.
 12. A tape printing apparatus as claimed in claim 1, wherein themarkings on the image receiving tape provide information as to thecharacteristics of the image receiving tape, said monitoring means beingarranged to detect different markings on different types of imagereceiving tape and to provide a signal indicative of the differentmarkings so that the characteristics of the image receiving tape areidentifiable.
 13. A tape printing apparatus as claimed in claim 12,wherein at least one of the following parameters varies in dependence onthe characteristics of the image receiving tape pitch of markings; widthof markings; color of markings; and reflectivity of markings, saidmonitoring means being arranged to provide a signal indicative of theparameters of the markings.
 14. A tape printing apparatus as claimed inclaim 12, wherein the characteristics of the image receiving tapecomprise at least one of the following parameters: tape width, tapebackground color, tape printing color, tape length, printing energy. 15.A tape printing apparatus as claimed in claim 12, wherein the controlmeans is arranged to control the operation of the tape printingapparatus in accordance with the identified tape characteristics.
 16. Atape printing apparatus as claimed in claim 1, wherein the drive systemis arranged to drive the image receiving tape backwards after a firstimage has been printed thereon, and when the image receiving tape isdriven forwards again by the drive system a second image is printed onthe image receiving tape overlying the first image, the markings on theimage receiving tape being used to position the image receiving tape sothat the first and second images overlie on another.
 17. A tape printingapparatus as claimed in claim 16, further comprising: counting means forcounting the number of markings which pass a given location when theimage receiving tape is driven past the printing means in the forwardsdirection and for counting the number of markings which pass the givenlocation when the image receiving tape is driven backwards, saidcounting means being arranged to stop the driving of the image receivingtape in the backwards direction by the drive system when the number ofmarkings which have passed the given location is substantially equal tothe number of markings counted when the image receiving tape is drivenpast the printing means in the forwards direction.
 18. A tape printingapparatus as claimed in claim 1, wherein the printing means comprises athermal print head having a group of printing elements to which pixeldata defining the image to be printed is passed sequentially on agroup-by-group basis by the control means, the groups being sequentiallyprinted adjacent one another in the direction of movement of the imagereceiving tape.
 19. A tape printing apparatus as claimed in claim 18,wherein the sequential printing of the image on the image receiving tapeis controlled by the control means in dependence on the speed of theimage receiving tape.
 20. A tape printing apparatus as claimed in claim1, wherein the driven system comprises a dc motor.
 21. A tape printingapparatus as claimed in claim 20, further comprising: speed controlmeans to control the speed of rotation of the motor to be at anapproximately constant level, the speed control means being coupled tothe monitoring means, whereby the speed of the motor is controlled independence on the detected speed of the image receiving tape.
 22. A tapeprinting apparatus as claimed in claim 21, wherein the speed controlmeans controls the speed of rotation of the motor to maintain theapproximately constant level by applying a maximum drive to the motor ifthe speed of the image receiving tape detected by said monitoring meansfalls below a first predetermined value, no drive if the speed of theimage receiving tape exceeds a second predetermined value and a lineardrive versus speed characteristic if the speed of the image receivingtape is between the first and second predetermined values.
 23. A tapeprinting apparatus as claimed in claim 1, wherein the monitoring meansis arranged to detect when a supply of image receiving tape is notpresent and to provide a signal indicative thereof.
 24. A tape printingapparatus as claimed in claim 1, wherein the monitoring means isarranged upstream of the printing means.
 25. A supply of image receivingtape arranged for use in a tape printing apparatus so that the imagereceiving tape can be driven past a printing location and an imageprinted thereon, the image receiving tape comprising a continuousprinting layer having a top printing surface for receiving a printedimage and a rear adhesive surface and a continuous backing layerremovable to uncover the rear adhesive surface of the top printinglayer, the image receiving tape carrying along its length regularlyspaced detectable markings to provide an indication of the speed atwhich the image receiving tape is driven past the printing location, incombination with a tape printing apparatus the tape printing apparatuscomprising: input means for receiving data defining an image to beprinted on the an image receiving tape; receiving means for receiving asupply of the image receiving tape; printing means for printing an imageon the image receiving tape in accordance with the input data; controlmeans configured to control the printing means; a drive system operableto drive the image receiving tape past the printing means; andmonitoring means for monitoring the speed of the image receiving tape,the monitoring means being arranged to detect markings provided on theimage receiving tape and to provide a signal indicative of the speed atwhich the image receiving tape moves past said printing means the signalbeing supplied to the control means for controlling the printing meansin dependence on the speed of the tape indicated by the signal.